The poor prognosis of patients with advanced gastric and esophageal cancer indicates an obvious need for more effective treatments. Based on a response rate approaching 50% in single institution trials, irinotecan- (CPT-11) cisplatin based therapy has been gaining support. However, responses are short lived and a high incidence of significant toxicity has been associated with this regimen. Based on the preclinical findings of others, documenting upregulation of topoisomerase I (Topo I) activity, the target enzyme for CPT-11, after administration of mitomycin C (MMC) and our observation that CPT-11 decreases the levels of DT-Diaphorase (NQ0R), we recently completed a pharmacologically designed phase I study of the combination. Low doses of MMC were used to modulate Topo I and CPT-11 activity. We demonstrated upregulation of expression of the Topo I gene in peripheral blood mononuclear cells (PBMC) after MMC administration, good tolerability and encouraging antitumor activity in patients with refractory solid malignancies that included patients with esophageal and stomach cancer. In this proposal, we plan to study advanced- and previously-untreated patients with esophageal and GE junction adenocarcinomas. A two arm, randomized, phase II trial will compare two schedules of sequential MMC and CPT-11 to pick the best of the two schedules for phase III evaluation. As a potential proof-of-concept in humans of the importance of NQ01 mutations, topoisomerase I and carboxylesterase gene expression, as predictors of chemoresistance to MMC and CPT-11, we will obtain tumor tissue and PBMC samples in order to evaluate possible associations between these genes, prognosis and antitumor activity.